Composite metallic powder



Patented Oct. 13 1942 COMPOSITE METALLIC POWDER Richard S. Reynolds, Richmond, Va., assignor to Reynolds Metals Company, Richmond, Va., a

corporation of Delaware No Drawing. Application March 16, 1940, Serial No. 324,343

Claims. (Cl. 106-290) This invention relates particularly to a new and improved composite aluminum and zinc, bronze, and other metallic p0 "i' aste, suitable for producing metallic paints and to methods of production therefor, and generally relates to conposite metal powders.

Heretofore', mixtures of aluminum powder and zinc powder have been utilized as pigments in suitable vehicles, such as oil or varnish, for bronze powder paints. However, due to the variance of the specific gravity of the metals, difficulties are encountered in commercial production runs, in obtaining uniform mixtures.

Brilliance and leafing are desired characteristics for bronze powds There are more or less standard processes for the production of aluminum bronze powders. Minute flakes of aluminum bronze powder ordinarily may have an average flake thickness of about .00002" and a single gram may contain roughly ten billion flakes of aluminum, of varying sizes. The flattened minute flakes when in a vehicle having a lighter specific gravity than the metal, nevertheless tend to leaf, namely, come to the surface of the vehicle, and form a practically continuous metal film, because of the shape of the particles and surface tension forces.

Zinc powder does not have the brilliance of aluminum powder, and while zinc flakes will leaf they do not leaf with the effectiveness or speed of the aluminum flakes. In ordina mixtures of aluminum andzip p wfifsifio iated in a paint vehicle vgen the paint is applied, the aluminum tends to rise to the surface more rapidly than the zinc and unless there is a high proportion of aluminum particles in the paint, the zinc particles fill in the empty spaces between the aluminum particles, destroying th brilliance of such mixed pigment paints. If the aluminum particles are present in such a high percentage as to form a practically continuous film of aluminum particles at the surface of the paint, the zinc particles are thoroughly blanketed. Therefore, mixtures of aluminum and zinc powders in flake form either with one or both of the powders stearated, have been difficult to produce because it has been impractical to obtain uniform mixtures and also unsatisfactory in use due to the lack of brilliance, unless preponderant quantities of aluminum flake are used.

Accordingly, it is an object of my invention to produce a new type of composite metallic flake particle, having a core 0 nc a. urfacaor aluminum an o prouce such flake particles from stficli'jfiliibmfdiiibfiss alummum lacketed zinc tonsvfiiffimr'rsgnfinite'tiild nd It'i alsd'vvitliiii the purview of this invention to form other composite metallic leafing flakes for paint pigments, and to produce the same from various appropriate composite metal foils where any desired appropriate surface metal is firmly jacketed to a core of another metal by an alloy bond.

It is a further object of my invention to produce a new product, namely, a substantially uniform bronze powder or paste which includes a substantial portion of aluminum surfaced zinc flakes of relatively high lustre due to the aluminum surface and which further may include zinc flakes and aluminum flakes.

It is a further object of my invention to form a composite metal powder containing aluminum surfaced zinc particles from an aluminum jacketed zinc foil where the core 'and jacket layers are firmly united by an alloy bond, and to form such composite metal powder by the usual processes for producing aluminum bronze powder, namely, by disintegration in a ball mill, or by the hammers of a stamping mill, in the presence of a lubbricant with subsequent polishing of such nature to produce stearic acid coated metal particles of excellent brilliance and leafing characteristics.

A further object of my invention is to produce a new metallic powder comprising a substantial amount of aluminum surfaced zinc flakes which will leaf when incorporated" into a paint vehicle, some zinc flakes and some fine aluminum flakes; such new intimately mixed composite powder tending to leaf with the result that metallic paint of high surface brilliance may be achieved due to the fine aluminum flakes and composite zinc and aluminum particles.

Other objects and advantages of my invention will become apparent from the following description of the invention, which is set forth merely for purpose of illustration. 0

It will be recognized that the essence of my invention revolves around the idea of the production of flat metallic flake particles suitable for use as pigments in metallic paints, by disintegrating composite metal foils formed of laminations of at least two layers of different metals which are bonded together by an alloy bond of metal and that one preferred laminated foil stock suitable for the practice of my invention consists in a zinc core foil cased on both sides with an aluminum jacket and united thereto by an aluminum zinc alloy bond.

Such aluminum and zinc composite foils may vary in the relative thickness of the aluminum and zinc layers and dependent upon variations in such thickness, different end products of metallic flake particles will be obtained, following disintegration.

For illustrative purposes, my invention will now be described in reference to a composite metal foil, comprised of zinc core cased on both sides with a jacket of aluminum and united thereto by a zinc and aluminum alloy bond. The casing may be approximately 10% by volume of aluminum on each side of the zinc core, but as indicated above, the thickness of the casings may vary. Such foil may vary from .010" to .0002" in thickness in the preferred practice of my invention.

The composite foil lends itselftobe processed into powder by'dfzfifdfi'fd methods similar to those used in producingaluminum metal powder from aluminum foil.

The composite foil may be first passed through a grinder or ch o ppgg tg reduce it to small pieceffor running in the hammer mills. The'sman'pise's of metal preferably should be subjected to a washing operation in which a hot solvent such as trichlorethylene, may be utilized for removing any surface oils. After the washing operation is completed and the foil is dried, the clean foil is introduced into a stamping mill with about of 1% of its weight of stearic acid, and the metal disintegrated to a fineness of approximately 20 to 30 mesh, commonly called flitters.

The flitters together with tailings from previous operations are then stamped further with small hammers, and additional stearic acid up to of 1% by weight may be added. The resultant powder will be screened to whatever mesh is required as is well understood in the art, and the tailings are returned for further disintegration with additional flitters. The fine powderisthen polished by means of the'hs'uaTpEilishing operations performed in making aluminum metal powder, preferably by placing the powder in an enclosed chamber adding stearic acid to the extent of about 1% by weig polishing by means of rotating brushes.

As an alternate mode of processing, disintegration might be carried on in a ball mill, and further, alternatively, the end products might be formed into a paste.

The powder produced by the illustrative example of my invention just given, comprises in the main, aluminum cased zinc metall ig flakes in which t a igprnum is subs g n ially co-extensivewith the n a; he'aluminum retains a pprgximately 1 g a"1' proportional thickness, so farashdeterminable. These composite aluminym and zinc particles have characteristics g ener a iiriilar to aluminum metallicppwder, father hey are of flake form of comparable thickness and size, possess the quality of leaflng to an excellent extent, and possess metallic lustre not equal, but approaching that of aluminum powder. The composite particles do not disintegrate due to the original aluminum and zinc alloy bond, which they retain at least in part.

In disintegrating the laminated aluminum zinc foil into lit'fill'fbillfdris "of flattened 'flake particles pergfamfjtis 'obvioustha t some very fine shredded particles of aluminum flake will be separated from the surface of the zinc and that also there will be some production of fine and also relatively coarse zinc flake, but the major end product is aluminum jacketed zinc flake.

When such a mixture is placed into the usual paint vehicle employed for conventional aluminum powders, all of the various particles tend to leaf and to give a composite intimately mixed metallic paint of excellent moisture proofing qualities and lustre. The fine lighter aluminum particles leaf most readily, giving a pleasing surface appearance, and the other metallic particles filling in the interstices forming what amounts to a continuous metallic film, wherein aluminum surfaces predominate.

Where any relatively coarse zinc particles are present to any degree, due to the nature of the foil disintegrated, they will normally tend to sink in the vehicle during the painting operation, where thawsbinhibitive action isdesirable, leaving the finer particles at the surface, thus giving good lustre.

It is within the purview of my invention to add quantities of aluminum powder to the end products of my process if desired. It is also within the purview of my invention to produce a composite metal pigment in flake form from various appropriate metals by conventional disintegration methods, wherein the composite pigment comprises metal flakes of at least two different metals, preferably bonded one to another by an alloy bond, where such pigments possess good moisture proofing qualities and are therefore desirable as a priming coat. Such priming coats would not fiecessarilyrequire the type of lustre and leafing qualities normally associated with aluminum bronze powder of standard commercial grades.

Those skilled in the metallic powder art will recognize that the essence of my invention involves the disintegration of metal foil stock into flattened flake particles by more or less standard disintegration processes where the foil stock comprises a core of one metal united to an outer jacket of a different metal by preferably a metal alloy bond, and that the preferred form of my invention involves the use of the core foil which is jacketed with aluminum and united thereto by an aluminum zinc alloy bond. However, it is obvious that certain steps of the described process may be utilized separately, or in whole or in part with other methods and processes to produce generally similar end products, and therefore reference to the appended claims should be made to determine the scope of my invention.

I claim:

1. A composite metal pigment of high lustre and good leafing properties formed by disintegrating an aluminum jacketed zinc foil stock which includes aluminum surfaced zinc particles, fine aluminum particles, and zinc particles.

2. A composite metal pigment of high lustre and good leafing properties formed by disintegrating an aluminum jacketed zinc foil stock which includes aluminum surfaced zinc particles wherein the aluminum is united to the zinc by an alloy bond of aluminum and zinc, and further includes fine aluminum particles and zinc particles.

3. As a new product, metallic powder of high lustre and good leafing properties which is a disintegrated product of zinc foil cased with aluminum and united thereto with an alloy bond of aluminum and zinc, and which includes minute flattened particles of zinc cased with aluminum.

4. As a new product, metallic powder of high lustre and good leafing properties which is a disintegrated product of zinc foil cased with aluminum and united thereto with an alloy bond of aluminum and zinc, and which includes minute flattened particles of zinc cased with aluminum, and further includes zinc particles and relatively fine aluminum particles.

5. As a new product, composite flattened metal particles of minute size suitable for use as pigment in metal paints, and having high lustre and good leafing properties wherein the particles comprise a zinc core surfaced with aluminum.

RICHARD S. REYNOLDS. 

